Try checking the channel list and see if the channel is listed multiple times but with different frequencies. Sometimes channel scans and guide data don’t match and can create multiple entries for a channel. If it’s listed multiple times you need to select the one with the correct frequency.

I checked the Channel List -no multiple entries.In any event,I removed it from the list and did a scan.

Now,it didn't find my VHF ch. 12.1 at all.

Even entering it directly just brings up the above error msg.

Addition -22.05.2013:

On the website of CHEX-TV today:

OVER THE AIR (OTA): We have had a technical issue with the switch to digital which negatively impacted some viewers - who otherwise would have received our signal. The cause has been identified and corrected. If you are currently having any difficulty receiving our signal, please call our engineering department for advice.

Today,I plugged my Tivo Box and TV back in upstairs,at my testing station in the bedroom(had thunderstorms for a few days,so I unplugged the lot!) and,lo and behold,entered "12.1" and ,viola!There it was,instantly!It even added itself to the Tivo's Channel list!

Mystery solved!

Last edited by Itproman : 05-22-2013 at 02:12 PM.
Reason: important update